Seasonal beers have been a part of brewing science and tradition for centuries. Think Christmas ale or May bock.

But to say one-off and specialty series products are the big thing in craft brewing right now would be a crazy understatement, as craft breweries release new and never-to-be-seen-again beers at a dizzying rate.

In Georgia, Athens’ Terrapin was an early instigator of the specialty beer game, starting with the Monster Beer Tour, featuring hefty seasonals such as Big Hoppy Monster. The Side Project series, begun in 2008, recently reached Volume 14 with Tomfoolery Black Saison.

Last year, Terrapin produced four beers in its Georgia Theatre Sessions series, plus the most recent Midnight Project collaboration with Left Hand Brewing and the annual Reunion beer for cancer research.

Owner/brewer Brian “Spike” Buckowski said 2010 was grueling but exciting, with Terrapin putting out some 20 specialty beers in addition to its regular year-round portfolio.

“It keeps everybody interested and it keeps your brand in focus,” Buckowski said. “With so many craft beers in the market now, you really need to put out something every couple of months to stay in the limelight.”

Terrapin’s Monster Beer spring seasonal, Monk’s Revenge Belgian-style double IPA, is coming soon, followed by Side Project 15, Indiana Krunkles wheat IPA, and Terrapin Twilight, a German kolsch-style in honor of the annual Athens bike race.

Atlanta’s Sweetwater has won the hearts of beer geeks with its experimental Dank Tank series. The most recent example is Mean Joe Bean, an imperial porter brewed with chocolate malt and coffee beans from Java Vino.

“According to the numbers, seasonal beer is what’s on fire,” said Sweetwater’s Steve Farace. “And limited edition beer is an extension of that. But this is fun stuff, especially for the brewers, and a lot of people are jumping on board.”

Last month, Atlanta’s Red Brick unveiled its new Brick Mason series with a limited edition 16th anniversary imperial brown ale aged in bourbon casks. Later this year, look for a Brick Mason double IPA.

Georgia’s newest and smallest craft brewery, Jailhouse in Hampton is set to release Midnight Special black ale, the first of its new Solitary Confinement series. It will be followed by Incarceration Belgian golden strong ale in July and Hop Riot double IPA later in 2011.

Owner/brewer Glenn Golden said limited edition beers are particularly challenging given Jailhouse’s tiny brewing and bottling capacity. But like other craft brewers, Golden believes the extra effort is worth it.

“Craft beer drinkers are looking for the newest and most interesting thing,” Golden said. “The idea of sharing a new and different beer is part of the camaraderie of craft beer. Experimenting with these beers is like being a home brewer again and that’s just a lot of fun.”